Plumb bobs



United States Patent PLUMB BOBS John Krasover, Philadelphia, Pa.

Application August 14, 1956, Serial No. 603,908

4 Claims. (Cl. 33-217) This invention relates generally to plumb bobs, and is particularly directed to new and useful impovements in adjustable-type plumb bobs.

The particular embodiment of the present invention, which is illustrated in the drawings and which will be described hereinafter in greater detail, comprises generally a reel mounted in a plumb-bob body for both rotating and shifting movement and adapted to carry a suspension line wound about the reel, and means for holding the reel against rotation in one position of reel-shifting movement, to thereby restrain the line against extension.

While there have in the past been provided various adjustable plumb-bob constructions having rotatable reels for carrying suspension lines, these prior devices have not found general acceptance and have been unsatisfactory for numerous reasons. For example, previous reel-type adjustable plumb bobs have been relatively complex in construction, expensive to manufacture and repair, and subject to frequent damage under normal conditions of use, so as to require a high degree of skill and care by the users. For these reasons, workmen on the whole have discarded reel-type adjustable plumb bobs and have reverted to the well-known pointed weight carried at one end of a string or line. This type of plumb bob usually requires a two-man operation, especially when the drop is relatively long, one man at the bob and another man to locate and adjust the length of the string at its fixed end.

Accordingly, it is a general object of the present invention to provide a reel-type adjustable plumb bob which overcomes the above-mentioned difiiculties and is capable of quick and easy use by a single person, requiring only a one-hand operation to adjust the plumb line to its desired length.

It is a further object of the present invention to provide an adjustable plumb bob having the advantageous characteristics mentioned in the foregoing paragraph, which is extremely simple in construction and durable in use, neat and attractive in appearance, and which can be manufactured and sold at a reasonable cost.

Other objects of the present invention will become apparent upon reading the following specification and referring to the accompanying drawings, which form a material part of this disclosure.

The invention accordingly consists in the features of construction, combinations of elements, and arrangements of parts, which will be exemplified in the construction hereinafter described, and of which the scope will be indicated by the appended claims.

In the drawings:

Figure l is a front elevational view showing a plumb bob of the present invention with the plumb-bob reel in a freely rotatable condition;

Figure 2 is a sectional elevational view taken substantially along the line 22 of Figure 1;

Figure 3 is a view similar to Figure 2, but showing the plumb-bob reel in its condition locked against rotation;

Figure 4 is a sectional view taken substantially along the line 44 of Figure 2;

Patented Aug. 26, 1958 Figure 5 is a transverse sectional view taken substantially along the line 5-5 of Figure 1; and

Figure 6 is a partial sectional view taken substantially along the line 66 of Figure 1.

Referring now more particularly to the drawings, the plumb bob of the invention illustrated therein comprises an elongate, hollow body, generally designated 10, arranged in the illustrated, vertical disposition in normal use. The hollow body 10 is advantageously formed of plastic material, as illustrated, but may be fabricated of other suitable material, if desired.

The plumb bob body 10 is of generally cylindrical configuration and is shaped with its lower portion 11 converging downwards toward a lower end wall 12, see Figure 2. The upper end of the body 10 is closed by a Wall 13 formed with a through aperture 14 located substantially axially of the cylindrical body. In the region intermediate and spaced between the lower and upper body end walls 12 and 13, the body 10 is formed with a pair of facing, generally rectangular front and rear cut-outs 15 and 16, respectively. The body portions remaining in the intermediate body region between the cutouts or openings 15 and 16 define a pair of laterally spaced, generally parallel side pieces 17. and 18 extending longitudinally of the body.

The body side pieces 17 and 18 are substantially identical each being formed with a longitudinally extending slot, as at 19 and 26, respectively, in Figure 4. That is, the slots 19 and 24B are located in laterally spaced registry with each other and extend longitudinally of the body 19. On the inner surfaces of the side pieces 17 and 18, adjacent to the upper ends thereof, are integrally formed or fixedly secured a pair of locking members or lugs 21 and 22. Stated otherwise, the locking members or lugs 21 and 22 extend on the inner faces of the side members 17 and 18, respectively, downward toward and terminate short of the associated side member slots 19 and 2%). As best seen in Figures 2 and 3, the lugs 21 and 22, which are identical, are each of generally trapezoidal elevational configuration, and include downwardly extending side edges converging toward and terminating in a generally horizontal lower edge. Thus, the ing 21 includes downwardly convergent side edges 26 terminating at a lower edge 27, while the lug 22, see Figure 5, includes downwardly convergent side edges 28 terminating in a horizontal lower edge 29.

Exteriorly on the lower body end 12 is provided adepending point 33 which includes a .boss 34. projecting upward through the body end wall 12; and, a relatively heavy mass or weight 35 is seated interiorly in the lower body reigon 11 and formed with a screw fastener or the like 36 extending into the boss 34. By this construction, the weight 35 is secured fastinteriorly of the lower body region 11, and the point .33 is secured fast onthe exterior of the lower body end wall 12.

Arranged transversely of and within the;plumb-'bob body 10, extending generally horizontally between the body side members 17 and 18, is a shaft, rod or pin 39. More specifically, the shaft 39 has its opposite ends extending through and rotatably received in the side member slots 19 and 20, and may beprovidedexteriorly .of the side members with retaining heads 40 and 41. A knurled knob 42 may be fixed on one end of the shaft 39, say on the retaining head 49 exteriorly of the body 10, for a purpose appearing presently. It will now be apparent that the shaft 39 extends transversely and generally horizontally through the plumb bob body 10 when the latter is in its normal vertical disposition and is journaled in the side member slots 19 and 20 for axial rotation therein. Further, the shaft 39 is shiftable longitudinally of the plumb bob body 10 in the slots 19 and 20, so as to be movable vertically toward and away from shiftable' therewith toward and away from the locking lugs 21 and 22. The spool flanges 46 and 47 are located at opposite ends of the spool and engageable with the locking lugs 21 and 22 upon shifting movement of the spool upward. Further, the peripheries of the spool flanges 46 and 47 are provided with ratchet-like teeth 48 and 49 engageable with the .lugs 21 and 22, respectively, to lock the spool 45 against rotation in one direction when the spool is shifted upward to engage with the lugs. Viewed otherwise, the teeth 48 of the flange 46 define in the spaces therebetween a plurality of periph eral flange notches 50, while the teeth 49 of the spool flange 47 combine to define intheir interspaces a plurality of peripheral notches 51. The thus defined spool flange notches serve to receive the lugs 21 and 22 when the spool is shifted upward to its locked position of Figure 3. It will there be seen that the ratchet-type teeth of the spool flanges engage with the side edges of the locking lugs, and that the lower edges of the locking lugs engage in the flange notches to limit upward movement of the spool.

In use, a flexible line or cord 53 is coiled about the spool 45 between the flanges 46 and 47 and extends upward therefrom slidably through and out of the upper wall aperture 14 of the body 10. The upper end of the 'line 53, which is broken away in the drawings, may be secured at alocation below which it is desired to find a plumb point.

The plumb bob body may then be manually or otherwise externally supported and lowered at a rate sufficient to withdraw or extend the line 53 out of the opening 14, by rotating the spool 45, but without elevating or shifting the spool upward. That is, relatively. slow downward supported movement of the body 10 will cause the unwinding string 53 to rotate the spool 45 without shifting the latter upward. When the point 33 of the plumb bob nears the intended lower reference level, the rate of downward movement of the body 10 may be increased, as by dropping orreleasing the'body to fall by its own weight. This relatively fast or accelerated downward movement of the plumb bob body causes the unwinding string 53 to elevate or shift the spool 45 upward into its upper limiting position, in which condition the flange teeth 48, 49. will engage with their re- If spective lugs 21 and 22 and be locked against further unwinding rotation of the spool. That is, the spool 45 unwinds during the relatively slow downward body movement in the direction of the arrows in Figure 2; and, further unwinding rotation of the spool is prevented when the spool is shifted upward by a sudden drop or relatively fast downward body movement, as the teeth. 48 and 49 are shaped to engage with an positively abutt against their respective lugs, as in the locked spool condition of Figure 3.

After the desired plumb point has been thus located, it is only necessary to rewind the line 53 on the spool 45, in the direction opposite to the arrows in Figure 2, as by manual rotation of the knob 42.

From the foregoing, it is seen that the present invention provides a substantially automatically adjustable plumb bob which fully accomplishes its intended objects and is well adapted to meet practical conditions of manufacture and use.

Although the present invention has been described in some detail by way of illustration and example for purposes of clarity of understanding, it is understood that certain changes and modifications may be made within the spirit of the invention and scope of the appended claims.

What is claimed is:

l. A plumb bob comprising an elongate normally vertically disposed hollow body, a reel mounted in said body for rotation about an axis transverse of said body and for limited free shifting movement longitudinally of said body, and holding means on said body located between said reel and the upper end of said body and engageable with said reel upon shifting movement of the latter to its limiting position toward the upper body end to hold said reel against rotation in said upper limiting position,

whereby a line coiled about said reel and extending up ward therefrom is adapted to be unwound by rotation of said reel when said body is lowered by an external Sup; port and said line is adapted to be locked against unwinding by dropping said body to cause shifting movement of said reel into its limiting position held against rotation. v

2. A plumb bob according to claim 1, said holding means comprising a lug fixed on said body and engageable in peripheral notches of said reel upon shifting movement of the latter toward said lug to prevent rotation of said reel.

3. A plumb bob comprising an elongate normally ver tically disposed hollow body, a shaft arranged transversely of and within said body intermediate the ends thereof and mounted therein for limited shifting movement longitudinally of said body, a reel mounted on said shaft for V rotation about the axis of the latter and shifting movement with said shaft longitudinally of said body, a suspension line wound about said reel and normally extending therefrom loosely through the upper body end for attachment to a support, and a locking lug fixed on said body adjacent to the upper end thereof and engageable with said reel upon shifting of the latter toward said upper body end to lock said reel against rotation, whereby said line is adapted to be unwound when said body is moved downward at a rate sufficient to cause rotation of said reel by said line without shifting said reel into its locked position and said line is adapted to be locked against unsufiicient to cause shifting movement by said line of said reel into its locked position.

4. A plumb bob according to claim 3, in combination with peripheral teeth on said reel engageable with said locking lug when said reel is in its locking position to positively hold said reel against rotation.

References Cited in the file of this patent 

